This invention relates generally to apparatuses for producing semiconductors and more particularly to improvements in the wafer centering mechanism in the wafer rotational processing device of a semiconductor fabricating apparatus.
As is known, in the production of various kinds of semiconductors, wafer rotational processing devices are used.
A conventional wafer rotational processing device has a wafer centering mechanism which generally comprises a wafer chuck in the center, a pair of wafer stops in mutually confronting state, and a shifting mechanism capable of moving these wafer stops in directions perpendicular to the direction of entrance of a wafer. A wafer is of circular disk shape, in general. The mutually confronting contact surfaces of the wafer stops are concave and are of semi-circular shape of a radius of curvature equal to one half of the outer diameter of the wafer to be processed as viewed in a direction perpendicular to the plane of the wafer.
When a wafer is fed into this wafer centering mechanism, and its center approaches the center of the wafer chuck, it is contacted by the semi-circular contact surfaces of the wafer stops approaching from their movable directions and is thereby clamped and centered. The organizational features and operation of this conventional wafer centering mechanism will be described in greater detail hereinafter with reference to a drawing.
In a conventional wafer rotational processing device with a wafer centering mechanism of the above described mechanical organization, the radius of curvature of the semi-circular contact surfaces of the wafer stops is fixed relative to the wafer diameter. For this reason wafers of different diameters could not be processed continuously in a mixed state.
Accordingly, it is an object of this invention to provide a semiconductor producing apparatus provided with a wafer centering mechanism capable of correctly centering continuously wafers of different diameters in mixed state for processing.